Voltage multiplier



4 Sheets-Sheet 1 EDGAR EVERHART NVENTORS Ms-JK# ATTORNEY PAUL LORRAiN(MQ/h May 26, 1959 E. EVERHART ET Al.

VOLTAGE MULTIPLIER Filed Feb. 25. 1954 May 26, 1959 E. EVERHART ET ALVOLTAGE MULTIPLIER 4 Sheets-Sheet `2 Filed Feb. l25. 1954llnlllllllllll/llllr rlllllllnv.

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EDGAR EVER HART PAUL LORRAIN INVENTOR ATTORNEY May 26, 1959 E. EVERHARTET AL 2,888,629

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l/UQM INVIENTORS ATTORNEY United States Patent C VOLTAGE MULTIPLIEREdgar Everhart, Storrs, Conn., and Paul Marie Lorrain,

Montreal, Quebec, Canada, assignors, by mesne assignments, to ResearchCorporation, New York, N.Y., a corporation of New York ApplicationFebruary 25, 1954, Serial No. 412,551

6 Claims. (Cl. 321-15) This invention relates to a voltage multiplyingcircuit which is an improvement over the conventional cascade voltagemultiplying circuit known in some quarters as the Cockcroft-Waltoncircuit.

The circuit of this general type was first described by H. Greinacher inZeits. f. Physik (1921), vol. 4, page 195, and has gone into widespreaduse. As is well known, such a circuit multiplies, rectifies and liltersalternating voltage applied thereto. It has however the disadvantagethat even when no direct current is drawn from the output, there is animportant loss in output voltage caused by circulating currents in thestray capacitances. In addition, where a current is drawn from such acircuit, there is ripple or periodic voltage fluctuation in the output,and the circulating currents referred to have the effect of increasingsuch ripple, which is frequently objectionable.

The present invention has two principal objects, namely, to providecascade voltage multiplying circuits wherein the output voltage closelyapproximates the theoretical voltage obtainable from such circuits (i.e.to improve the voltage efficiency), and to minimize ripple in such acircuit.

Y Other objects and numerous advantages will be apparent to one skilledin the art from an examination of the entire specification and theaccompanying drawings.

The theory behind this invention has been set out in an article by thepresent inventors:

The Review of Scientific Instruments, vol 24, No. 3, pp. 221-226, March1953, The Cockcroft-Walton Voltage Multiplying Circuit, by EdgarEverhart and Paul Lorrain.

In examining the above publication, attention is directed to thefollowing points:

(l) In Figure 7 on page 225 of the publication, a capacitor, inductanceand resistor are shown in the upper right-hand corner, directly abovethe terminal denoted as H.V. While these components are used in thecalculations set out in the publication, they are not of any signicance,because they are not connected at their righthand end and accordingly donot have any function in a practical device, and would not be used in anactual circuit.

(2) In Table I on page 224 of the publication, component values aregiven for a 500 kilovolt voltage multiplier used as an accelerator, butmore appropriate and complete values have now been found and will be setout herein, under the heading Example The present invention, while ofgeneral application, is particularly suited for providing a high voltagefor ion accelerators or for television circuits.

The invention will now bedescribed with the assistance of theaccompanying drawings, wherein preferred embodiments are shown. It willbe realized that changes can be made without departing from the scope ofthe invention as defined in the appended claims, and the embodimentsshown and described are to be construed by Patented May 26, 1959 way ofexample and not in limitation of the invention.

In the drawings:

Figure 1 shows a side elevation view of an embodiment of an ionaccelerator using the cascade voltage multiplying circuit describedherein;

Figure 2 shows a cross-sectional view as along the line 2--2 in Figure1;

Figure 3 shows a side elevation view of one of the capacitors denoted by6 in Figures 1 and 2;

Figure 4 shows a fragmentary elevation cross-sectional view of thecenter portion of said capacitors 6 and part of an adjacent spacerdenoted by 7;

Figure 5 shows a fragmentary cross-sectional view of substantiallyone-half of Figure 3, so as to better disclose the construction ofcapacitor 6;

Figure 6 shows a circuit diagram of one embodiment of the voltagemultiplying circuit disclosed herein;

Figure 7 shows a further form of the circuit shown in Figure 6, which isparticularly eiective in eliminating ripple;

Figure 8 shows a further embodiment of the circuit of Figure 7 where oneor more intermediate loading coils are used to further improve thevoltage etliciency;

Figure 9 shows another embodiment of the circuit capable ofaccomplishing the result of that shown in Figures 6, 7 and 8, withalmost complete elimination of ripple;

Figure 10 shows the manner in which various power supplies incidental tothe device of Figures 1 and 2 may be conveniently obtained from thevoltage multiplying circuit which is the subject of the presentinvention, apart from the high-voltage output to which end the saidcircuit is particularly intended; and

Figure l1 shows a preferred manner of feeding the filaments of the tubesforming part of the voltage multiplying circuit of the presentinvention.

Referring now to the drawings, wherein the like parts are denotedthroughout by similar reference numerals, and with particular referenceto Figure 1, a preferred form of the present invention is shown inassociation with an ion accelerator. The ion accelerator tube (whichforms no part of this invention) is shown at 1 standing on a basedenoted by 5. Ion accelerator tube 1 has rings thereon denoted by 3which are effectual in eliminating corona. A high voltage dome denotedby 4 is attached to the end of ion accelerator tube 1 opposite base 5,the purpose of which is also to eliminate corona.

The voltage multiplying circuit contemplated by the present inventionmakes use of a plurality of diode electronic tubes and a plurality ofcapacitors, with certain other components. In Figures 1 and 2, the mostimportant parts of the voltage multiplying circuit are visually evident.The capacitors, denoted by 6, are held in proper spatial relationshipwith one another by means of spacers denoted by 7. The tubes, denoted by8 are mounted adjacent capacitors 6, and tubes 8 are provided withsuitable anti-corona shields denoted by 9,and 10 which are known in theart.

A source of alternating current is connected to the cascade voltagemultiplying circuit about to be described, and from such alternatingcurrent the multiplying circuit produces a high voltage direct currentwhich is made use of in the ion accelerator tube 1.

The structural details of the device can be seen with particularreference to Figure 2, wherein it is seen that the elements justdescribed are held in place by means of la beam of dielectric materialssuch as Lucite, denoted by 11. Auxiliary guides denoted by 12 areattached to beam 11 for supporting the cascade voltage multiplyingcircuit. 4

As can be seen in Figure 2, the voltage multiplier is in the form of twobanks of capacitors, with a. bank of tubes along the lower part of thedevice, and equidistant from the two banks of capacitors.

The capacitors 6 are shown with particular reference to Figures 3, 4 and5. Condensers 6 comprise two circular metal plates denoted by 13 and 14separated by two films of dielectric material. The dielectric filmattached to plate 13 is denoted by 15 and the dielectric film attachedto plate 14 is denoted by 16.

As seen in the drawings, each of the plates 13 and 14 has a rolled lipdenoted by 17 and 18 respectively.

It is contemplated that the dielectric films 15 and 16 attached toplates 13 and 14 respectively, will be in the form of circular envelopesmoulded around the said plates. It has been found satisfactory if thedielectric film is made of polyethylene, and for condensers of diameterof the order of nine and a half inches, six layers of polyethylene eachof five mils thick have been found satisfactory.

Capacitor plates 13 and 14 are circular in shape, and have attached attheir centers smaller circular plates denoted by 19 and 20 which may bemerely cemented to plates 13 and 14 respectively, since no electricalconnection therebetween is necessary. Spacers 7 are adapted to slideover circular plates 19 and 20, and it is accordingly possible to stacka substantial row of capacitors 6, maintaining them in proper spatialrelationship.

In order that the capacitance of condensers 6 may be carefullycontrolled, dielectric clamps denoted by 21, of a general C-shape areadapted to fit over each pair of capacitor plates 13 and 14 and theirassociated lms, so as to press the plates firmly together.

It is contemplated that four of such clamps 21 will be provided on eachcapacitor 6, although the present invention is not in any way restrictedto such number, or such construction. It is apparent that adjustableclamps could be used if it should prove necessary to adjust thecapacitance of capacitors 6, which for conditions of operationheretofore experienced, has not been found necessary.

Referring now to Figure 6, one forrn of the circuit will now bedescribed. The left-hand side of Figure 6 is quite conventional andcomprises an input transformer formed of coils 61 and 62, which areconnected to a capacitor denoted by 63 and a tube denoted by 64.Capacitor 63, and all other capacitors in this figure may be similar tocapacitor 6 already described. There are a number of identical stages,wherein there is always a capacitor connected between the anode of atube and the cathode of the tube of the following stage, assuming apositive output is required as is the case where the use is inconnection with an ion accelerator as shown in Figure 1. It will berealized that if a negative output were required, the circuit would besimilar to that shown in Figure 6, except that the anode and cathode ofeach of the tubes would be reversed.

There may be as many stages as desired, and the present invention is inno way limited to the number of stages except as necessitated bypractical considerations. At the last stage there is a tube denoted by65.

At the output, between the anode and cathode of tube 65 is connected acapacitor denoted by 66, and an inductance denoted by 67. The highvoltage output is obtained at the end of inductance 67 adjacent thecathode of tube 65.

It will be seen that the circuit shown in Figure 6 differs fromconventional cascade voltage multiplying circuits in that a capacitanceand inductance (66 and 67, respectively) are provided across the lasttube 65.

Referring now to Figure 7, it will be seen that this embodiment issimilar to that of Figure 6, having elements denoted by 71-77 which aregenerally similar to elements 61-67, respectively, of Figure 6,including a transformer coil denoted by 72 and an output inductancedenoted by 77. In Figure 7, transformer coil 72 is centertapped at 78and connected to ground, and inductance 77 is also center-tapped. It isfrom the center-tap of inductance 77 that the high-voltage output istaken. With the present form of the invention, ripple is almostcompletely eliminated.

Referring now to Figure 8, it will be seen that this circuit is similar'to that shown in Figure 7, having elements denoted by 81-88 which aregenerally similar to elements 71-78, respectively, of Figure 7. InFigure 8, the transformer coil denoted by 82 is center-tapped at 88 andconnected to ground and the output inductance denoted by 87 is alsocenter-tapped, from which point the high-voltage output is taken. Thedifference from Figure 7 is the provision of an intermediate loadingcoil denoted by connected as shown substantially midway between theinput and output of the circuit. The loading coil 80 has in seriestherewith a capacitor denoted by 89.

The use of a loading coil such as loading coil 80 greatly improves thevoltage efliciency. It is important to note that more than one suchloading coil may be similarly connected between input and output.

Referring now to Figure 9, it will be seen that there are again elementsdenoted by 91-95 similar to elements G11-65, respectively, of Figure 6,and also that the present embodiment differs from the conventionalcascade voltage multiplying circuit, in that there is provided aninductance denoted by between the secondary of the input transformerdenoted by 92, and the capacitor 93 connected to the cathode of thefirst tube denoted by 94.

Similar inductances denoted by 97 and 99 are similarly connected in eachstage. Assuming a positive output is required, the high-voltage outputis taken from the cathode of the last stage, it having already beenmentioned that the polarity of the output can be made negative if theanodes and cathodes of the tubes are reversed with respect to the formshown in the present disclosure.

The embodiments shown in Figures 8 and 9 carry out the principal objectsof the invention in providing a voltage output which closelyapproximates a calculated value being not appreicably decreased bycirculating currents, and also materially suppress ripple.

Referring now to Figure 10, a convenient manner of obtaining powersupplies for various parts of the ion accelerator of Figures 1 and 2will now be described. In the type of ion accelerator mentioned, avoltage for the ion source of the order of 1000 volts and a voltage forthe extraction electrode of the order of 15,000 volts are required,apart from the high-voltage output for accelerating purposes. The firsttwo are conveniently obtainable with the circuit as shown in Figure 10.

In Figures 7 and 8 the output inductances 77 and 87, respectively, arecenter-tapped.

In Figure 10, the inductance shown at 1007 corresponds to inductances67, 77 and 87 of Figures 6, 7 and 8 respectively, and while inductance1007 is shown centertapped as in Figures 7 and 8, this feature is notnecessary to the operation of the circuit of Figure l0.

On the right-hand side of inductance 1007, a half-wave rectifier isprovided, the principal component of which is a diode denoted by 1011. Acapacitor denoted by 1012 and a resistor denoted by 1013 are used in aconventional manner and the output for the extraction electrode isobtained at 1014 and 1015, being positive and negative respectively.

At the central and left-hand side of inductance 1007, a full-waverectifier is provided, the principal component of which is a full waverectifier tube denoted by 1016. The filament supply of tube 1016 isobtained from a coil denoted by 1017, inductvely linked to inductance1007. The output is taken at 1018 and 1019 being positive and negativerespectively, and in the output lines a resistor denoted by 1020 andcapacitors denoted by 1021 and 1022 are provided. The output at 1018 and1019 is for the ion source. i

The manner of supplying the filaments of tubes such as 64, 65; 74, 75and 94, 95 in Figures 6, 7 and 8, respec- 'as'ssgeae tively will now bediscussed ,withI reference to Figure 11'.

In the foregoing figures the cathodes have not been particularlyreferred to, but it has been found desirable to use ordinary filaments,such as are found in tubes of the 5825 type. The tubes are denoted by1104 in Figure 11,to indicate the similarity to tubes such as 64 inFigure 6. The filament of each tube 1104 is connected to the cathode ofthe adjacent tube 1104 and on the same side of the filament, connectionis made through'` the primary of a filament transformer denoted vby 1105to one of the capacitors 6, the said primary 1105bein'g tuned to theapplied radio-frequency with a capacitor denoted by 1106. The secondaryof the `filament transformer denoted by 1107 is connected at one endthereof to the side of the primary adjacent the filament, and the otherside of the secondary 1107 is connected to the opposite side of the saidlament. A, y

Since the device operates at high frequency, the tubes 1104 pass anappreciable current due tovtheir stray capacitance and this current willow through primary 1105 and the filament will be fed by thesecondary'1107. l

The values of the added components contemplated by this invention willnow be discussed.

In Figures 6, 7 and 8, the values of inductances 67, 77 and 87respectively, as indicated in the publication referred to above at page224, equation (26) are repre sented by, i

Lopt=Wb COth *21% where Lopt is the optimum value for such inductances;

W is the frequency in radians per second of the high frequency appliedto the input;

C is the total effective shunt capacitance per stage including therectifier and stay capacitauces; e.g. in Figure 6 in the rst stage, C isthe interelectrode capacitance of diode 6 plus the stray capacitances;

b is a constant such that the capacity of a condenser 6 is B2C;

N is the number of stages.

The values of the capacitors 63, 73 and 83 and the other capacitors ineach circuit will now be discussed. It is apparent that this inventioncontemplates equal series capacitance per stage. Referring to the abovepublication, particularly Figure 5 thereof and the text in connectiontherewith, in order to achieve equal series capacitance per stage,capacitor 63 will have double the capacitance of Ithe following orintermediate capacitors which will be equal among themselves. Capacitor66 will, again, have twice the value of the intermediate capacitors andwill have the same value as capacitor 63.

An example of a practical construction of a device according to Figure 1will now be given to illustrate the above, as well as other facts whichwill be apparent.

Example A device according to Figure 6 was constructed with a 20,000volt r.m.s. radio frequency input of 34 kilocycles capable of deliveringa nominal voltage of 500 kilovolts using 24 stages instead of the fourstages shown therein. The diodes such as diode 4 were of the R.C.A. No.5825 type, and the interelectrode capacitance plus stray capacitance perstage was 6.3 auf. The series capacitance per stage was 7O0Mtf. It isapparent that with 24 stages, 25 capacitors would be used, and thecapacitor corresponding to capacitor 64 in Figure 6 had a value equal totwice the series capacitance per stage, i.e. 1400 auf. Owing to thecommercial unavailability of capacitors having these values, the specialcapacitors as shown in Figures 3-5 were used.

The value of b was thus The inductance 67 was made up of two segmental Aair Acore coils having an inductance of 0.24 henry, each with oneportion short-circuited and as used in the present example, coil 67 wasa model 35 kv. coil manufactured by the Spelmann Television Company.

, The calculated value of Lm from the equation given above is,

Loot

=0.40 henry It will be seen that the device herein described is verysuitable for producing a high voltage for various uses includingaccelerator use, and is simple and convenient to build and maintain.

What is claimed is:

. l. A voltage multiplying circuit capable of converting energy at lowvoltage and high frequency to high voltage direct current, comprising aseries of stages, each stage consisting of a diode electron dischargedevice with a capacitor connected to one side of said diode, the inputpoints of each stage being Iat the side of said diode not connected tosaid capacitor and at the side of said capacitor remote from said diode,each of said stages being connected to the following stage in suchmanner that the side of the diode having a capacitor connected theretoof onestage is connected to the side of the diode not having a capacitorconnected thereto of the following stage, and comprising in addition aninductance load inserted in the circuit and effectively neutralizing theshunting capacitance of said stages across said high-frequency source toimprove voltage eiciency and eliminate ripple.

2. A device according to claim l wherein the input to the irst stage isthe secondary of a high frequency transformer, the device having inaddition a capacitor and inductance in series across the diode of thelast stage, the last-mentioned capacitor being connected to tha side ofthe diode of the last stage which is directly connected to the diode ofthe second-last stage, the lastmentioned inductance being connectedbetween the side of said lastmentioned capacitor remote from said diodeof the last stage and the other side of said diode of the last stage.

3. A voltage multiplying circuit capable of converting energy at lowVoltage and high frequency to high voltage direct current, comprising aseries of stages, each stage consisting of a diode electron dischargedevice with a capacitor connected to one side of said diode, the inputpoints of each stage being at the side of said diode not connected tosaid capacitor and at the side of said capacitor remote from said diode,each of said stages being connected to the following stage in suchmanner that the side of the diode having a capacitor connected theretoof one stage is connected to the side of the diode not having acapacitor connected thereto of the following stage, and comprising inaddition inductance means inserted in the circuit to improve voltageefficiency and aliminate ripple and having an inductance valuesubstantially equal to where W is the frequency in radians per second ofthe voltage applied to the input, b is a constant, C is the totaleffective shunt capacitance per stage including the diode and straycapacitances and N is the number of stages.

4. A voltage multiplying circuit capable of converting energy at lowvoltage and high frequency to high voltage direct current, comprising aseries of stages, each stage consisting of a diode electron dischargedevice with a capacitor connected to one side of said diode, the inputpoints of each stage being at the side of said diode not connected tosaid capacitor and at the side of said capacitor remote from said diode,each of said stages being connected to the following stage in suchmanner that the side of the diode having a capacitor connected theretoof one stage is connected to the side of the diode not having acapacitor connected thereto of the following stage, and comprising inaddition inductance means inserted in the circuit to improve voltageefciency and eliminate ripple, said secondary being center-tapped andgrounded vand the inductance being connected across .the diode of thelast stage is also center-tapped, the high voltage output beingavailable at said last-mentioned point.

5. A voltage multiplying circuit capable of converting energy at lowvoltage and high frequency to high voltage direct current, comprising aseries of stages, each stage consisting of a diode electron dischargedevice with a capacitor connected to one side of said diode, the inputpoints of each stage being at the side of said diode not connected tosaid capacitor and at the side of said capacitor remote from said diode,each of said stages being connected to the following stage in suchmanner that the side of the diode having a capacitor connected theretoof one stage is connected to the side of the diode not having acapacitor connected thereto of the following stage, and comprising inaddition inductance means inserted in the circuit to improve voltageeciency and eliminate ripple, said inductance means consisting of aninductance in each stage connected to the capacitor of each stage on theside of said capacitor remote from the diode of each stage, the highvoltage output being avail- 8 able at the side of the diode of the laststage connected to the capacitor of the last stage.

6. A voltage multiplying circuit capable of converting energy at lowvoltage and high frequency to high voltage direct current, comprising aseries of stages, each stage consisting of a diode electron dischargedevice with a capacitor connected to one side of said diode, the inputpoints of each stage being at the side of said diode not vconnected tosaid capacitor and at the side of said capacitor remote from said diode,each of said stages being connected to the following stage in suchmanner that the side of the diode having a capacitor connected theretoof one stage is connected to the side of the diode not having acapacitor connected thereto of the following stage, and comprising inaddition inductance means inserted in the circuit to rimprove voltageeiiiciency and eliminate ripple, wherein there is connected across thediode of an intermediate stage of said series of stages an inductanceand capacitance in series, and further including an inductance and acapacitance connected in series,'said inductance and capacitance beingconnected across Athe diode of an intermediate stage of said stages.

References Cited in the file of this patent UNITED STATES PATENTS1,666,473 Slepian -c Apr. 17, 1928 2,045,034 Kunte June 23, 19362,621,302 Friend Dec. 9, 1952

